1. Field of the Invention
The invention relates to a power management interface, and more particularly to a power management interface using a digitized approach.
2. Description of the Related Art
FIG. 1 shows a conventional power management circuit for a load. Referring to FIG. 1, the power management circuit is coupled to an alternating current (AC) power line VAC through terminals L and N. The power management circuit comprises a tri-electrode AC (TRIAC) switch 90, a gate triggering circuit 92, and a load 95. The gate triggering circuit 92 generates a trigger signal to control turned-on and turned-off states of the TRIAC switch 90. By adjusting a resistance value of an RC circuit within the gate triggering circuit 92, the turning off time of the TRIAC switch 90 can be controlled by the trigger signal. Referring to FIG. 2, when the trigger signal turns on the TRIAC switch 90, the waveform of a power line signal VTR tracks the waveform of the voltage signal on the AC power line VAC. When the trigger signal turns off the TRIAC switch 90, the voltage signal on the AC power line VAC can not be provided to the load 95, so that the power line signal VTR is switched to a zero level. Thus, when the trigger signal turns off the TRIAC switch 90, the power is not delivered to the load 92. According to the control to the state of the TRIAC switch 90, the power delivered to the load 92 is managed.
However, the drawback of the conventional power management circuit can not be applied for an electronic product whose front-end circuit comprises a bridge rectifier and a capacitor because of the rippling-wave effect of the capacitor. The conventional power management circuit of FIG. 1 is applied only for a resistance load. Further, because the power line signal VTR is switched from the zero level to the waveform of the voltage signal on the AC power line VAC, the conventional power management circuit of FIG. 1 has the poor power factor and high current harmonic, resulting in large power transmission loss.